The present invention relates to the suppression of unwanted modes of oscillation present in the resonant cavity of separable-insert coaxial magnetrons.
As has been indicated, during the development of standard separable-insert coaxial magnetrons, one of the major problems has been the difficulty of obtaining a low TE.sub.121 Q. Unwanted modes of oscillation, such as the TE.sub.121, present in the external resonant of `stabilizing` cavity were not being effectively removed or suppressed. For example, although the VMS-1009 magnetron, developed by Varian Associates, Inc. and now known as the VMS-1104, employed a standard step choke for TE.sub.121 suppression, little or no energy is coupled into its absorber.
The present invention fundamentally provides an optimum arrangement for effectively resolving this particular difficulty. This arrangement, although primarily applicable to the standard TE.sub.121 chokes and to particular magnetron designs, also is capable of suppressing other unwanted resonant cavity modes and it also can be adapted for use in other magnetrons.
According to the present invention, a flexible metal gasket is placed directly next to the ceramic shell to short the impedance of the kovar sealing strip and permit excitation of the standard choke arrangement. The use and placement of this gasket relative to other structural components is predicated upon a thorough analytical study of the prior art difficulties and a resulting appreciation of the basic cause of the problem.